Electronic musical system with magnetic field responsive switch and volume control

ABSTRACT

An electronic musical system has a DC power supply and a tone generator with a first resistance connected in series between them. A second resistance has one end connected to the series circuit between the power supply and the tone generator and the other end connected to ground. One of the resistances is a magnetoresistor the electric resistance of which varies in accordance with the intensity of the magnetic field applied thereto. A key is movably mounted above the magnetoresistor with a magnet element mounted thereon close to the magnetoresistor, so that movement of the key controls the electrical resistance of the magnetoresistor depending on the amount the key is moved, and thus controls the volume of the tone generator.

United States Patent [72] Inventor Mikio Ogi Hamamatsu-shi, Japan [21]Appl. No. 809,800 [22] Filed Mar. 24, 1969 [45] Patented June 29, 197173] Assignee Nippon Gakld Seizo Kabushiki Kaisha Hamamatsu-shi;Shizuoka-ken, Japan [32] Priority Mar. 29, 1968, Mar. 29, 1968 [33]Japan [31] 43/25029 and 43125030 [54] ELECTRONIC MUSICAL SYSTEM WITHMAGNETIC FIELD RESPONSIVE SWITCH AND VOLUME CONTROL 7 Claims, 8 DrawingFigs. [52] US. Cl 84/126, 84/1 .08, 84/1 1 7, 307/88, 335/2, 338/32 [51]Int.Cl 61% 1/02 [50] 84/ 1 .0 1, 1.09, 1.1, 1.13-1.15, 1.26, 1.27,423,427, 4 33, 439, 440, 1.28; 307/259, 309; 323/94 H [56] ReferencesCited UNITED STATES PATENTS 2,878,708 3/1959 Hanert 84/108 PrimaryExaminerD. F. Duggan Assistant Examiner- U. Weldon A!r0rneyWenderoth,Lind & Ponack ABSTRACT: An electronic musical system has a DC powersupply and a tone generator with a first resistance connected in seriesbetween them. A second resistance has one end connected to the seriescircuit between the power supply and the tone generator and the otherend connected to ground. One of the resistances is a magnetoresistor theelectric resistance of which varies in accordance with the intensity ofthe magnetic field applied thereto. A key is movably mounted above themagnetoresistor with a magnet element mounted thereon close to themagnetoresistor, so that movement of the key controls the electricalresistance of the magnetoresistor depending on the amount the key ismoved, and thus controls the volume of the tone generator.

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- BYMuJaII/LIXLL U ELECTRONIC MUSICAL SYSTEM WITH MAGNETIC FIELDRESPONSIVE SWITCH AND VOLUME CONTROL BACKGROUND OF THE INVENTIONGenerally, electronic musical instruments are provided with tonegenerators and switches which control the outputs of said tonegenerators. Accordingly, many electric contacts are necessary forelectronic musical instruments, and as the electric contacts,metal-to-metal contacts or metal-to-conductive rubber contacts are used.However, these are liable to cause miscontacts owing to the formation ofsulfides or oxides of metals or deposits of dust on the surfaces of thecontacts, and therefore they are unreliable. Moreover, said contacts canonly switch electric signals on and off and it is impossible to vary thevolume of sound in proportion to the strength with which the key isdepressed.

SUMMARY OF THE INVENTION A principal object of the present invention isto provide a keying device for electronic musical instruments with whichit is possible to effect a so-called touch-sensitive control withoutusing an electric contact in switching the output of a tone generator.That is, the keying device of the present invention is able to controlthe volume of the sound in response to the strength with which the keyis depressed.

Another object of the present invention is by utilizing thecharacteristics of a magnetoresistor which causes the electric currentflowing through the element to vary in response to the intensity of theapplied magnetic field, to provide a keying device for electronicmusical instruments which comprises a magnetoresistor connected betweena DC electric power source and a tone generator and forming part of apotential divider, and either the magnetoresistor or the magnet ismounted on a key and the other one of them is mounted on a stationarypart so that they cooperate with each other, whereby the magnetic fieldapplied to said magnetoresistor is varied by the manipulation of the keyso as to control the sound volume in response to the depression ofeachkey.

Still another object of the present invention is to provide a keyingdevice for electronic musical instruments comprising twomagnetoresistors connected between an electric power source and a tonegenerator as a potential divider, and further one of said twomagnetosensitive elements or a magnet is mounted on a key and the otherone of them is mounted on a stationary part so that they cooperate witheach other, whereby the magnetic field applied to said twomagnetoresistors is varied in response to the manipulation of the key soas to control the sound volume.

The magnetoresistor used in the embodiments of the present invention isone the electric resistance of which increases as the intensity of theapplied magnetic field increases.

Other objects and advantages of the invention will appear more fullyhereinafter from a consideration of the detailed description whichfollows, taken together with the accompanying drawings wherein severalembodiments of the invention are illustrated. It is to be expresslyunderstood, however, that the drawings are for the purpose ofillustration and description only and are not designed as a definitionof the limits of the invention, reference being had for this purpose tothe appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a circuit diagramillustrating the principle of a keying device according to theinvention;

FIG. 2 is a vertical cross-sectional view of a keyboard having thereonan embodiment of a keying device according to the invention;

FIG. 3 is an enlarged perspective view of the main part of theembodiment of FIG. 2;

FIG. 4 is another circuit diagram illustrating another embodiment ofakeying device according to the invention;

FIG. 5 is an enlarged perspective view of the main part of the keyingdevice of the embodiment shown in FIG. 4;

FIG. 6 is a vertical cross-sectional view of a keyboard fitted with amultiple keying device according to the invention;

FIG. 7 is a circuit diagram illustrating a further embodiment of akeying device according to the invention; and

FIG. 8 is a vertical cross-sectional view of a keyboard having thereonthe embodiment shown in FIG. 7.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the FIGS., reference numberI designates a DC electric power source the details of which areomitted, and the numbers 2,2, 2a and 2b designate magnetoresistors,respectively. Reference number 4 designates a tone generator the detailsof which are omitted. The output and hence the volume of sound producedis proportional to the power supplied to it. Reference numbers 5 and 5designate magnets.

In FIG. 1, a magnetoresistor 2 is connected in series between theelectric power source 1 and a power input terminal 21 of the tonegenerator 4, and a fixed resistor 3 is connected between the output sideof the magnetoresistor 2 and ground, and a potential divider is formedby said magnetoresistor 2 and the fixed resistor 3. Said tone generator4 has an output terminal 22. Said magnetoresistor 2 has an electricresistance which increases as the intensity of applied magnetic fieldincreases. The intensity of the magnetic field of said magnet 5 appliedto the magnetoresistor 2 becomes the maximum when the key is in the offstate and the intensity of the magnetic field of said magnet 5 becomesless or zero when the key is in the on state, thus no sound is producedwhen the key is in the off state, because the electric resistance of themagnetoresistor 2 is a maximum, and the power is not supplied to thetone generator 4. On the contrary, a sound is produced when the key isin the on state, as the electric resistance of the magnetoresistor 2becomes less and the power is supplied to the tone generator 4. When thekey is pushed down a small amount, the amount of power supplied to thetone generator 4 is small, and when the key is pushed down to a largeextent, the amount of power supplied to said generator 4 becomes larger,whereby so-called touch-sensitive control can be attained.

FIGS. 2 and 3 illustrate the positions of said magnet 5 and themagnetoresistor 2, wherein the magnet 5 is horseshoe shaped and ismounted by a screw 8 on a key 6 with nonmagnetic spacer 7 between it andthe key, and the magnetoresistor 2 is fixed to a holding block 10 whichis mounted on the keyboard frame 9. Consequently, the magnetoresistor 2is fixed and the magnet 5 moves with the movement of the key 6. Themagnet 5 and the magnetoresistor 2 are positioned as near to each otheras possible, with the best arrangement being as shown in FIG. 3, that isthe magnetoresistor 2 is between the north pole and the south pole ofthe magnet 5, and the intensity of the magnetic field of the magnet 5becomes a maximum when the key 6 is in the off state and becomes less orzero when the key 6 is in the on state.

FIG. 4 shows a circuit diagram of another embodiment according to theinvention, wherein the magnetoresistor 2 and the fixed resistor 3 inFIG. I have been substituted for each other. When the magnetoresistor 2is similar to that of FIG. 1, wherein the intensity of the magneticfield of the magnet 5 applied to the magnetoresistor 2 becomes a minimumwhen the key is in the off state, and the intensity of the magneticfield of the magnet 5 applied to the magnetoresistor 2 becomes largerwhen the key is in the on state, then the same result as in the case ofFIG. 1 is attained.

Furthermore, if the magnetoresistor is replaced by a magnetosensitivediode, the electric current through the diode is varied according to thedirection of the applied magnetic field, and almost the same results areobtained as when a magnetoresistor is employed. FIG. 5 illustrates anexample of a specific keying device by which a large control ratio canbe obtained by utilizing the characteristics of a magnetosensitivediode. That is, a magnetosensitive diode 2' is used, said diode 2 beingmovable between poles of a multipolar magnet 5 having the polarities asshown in FIG/5, wherein when the key is in the on state the magnet ispositioned to apply the magnetic field in the direction to permitelectric current to flow through the magnetosensitive diode 2' and whenthe key is in the off state the magnet is positioned to apply themagnetic field in the direction not to permit current to flow throughthe magnetosensitive diode 2'. According to this device, there is nofear of producing a signal leakage when the key is in the off state.

FIG. 6 illustrates an example of a keyboard comprising multiple keyingdevice having a plurality of magnetoresistors and a multipolar magnet.Said magnetoresistors 2, 2, are mounted on a holding block 10 atsuitable distances from each other and said holding block 10 is mountedon the keyboard frame 9. The multipolar magnet 5' is fixed to a springholder I V 12 through spring plates 11 so as to be driven directly orindirectly by a driving piece by the action of the key 6, and saidspring holder 12 is fixed to the keyboard frame 9. The magnet 5' andeach magnetoresistor 2 are positioned as near to each other as possibleand the intensity of the magnetic field to the multipolar magnet 5applied to each magnetoresistor 2 becomes the maximum when a key is inthe off state and becomes less or zero when the key is in the on state.F urthermore, when each element is a magnetosensitive diode, and when itis used such that the direction of magnetic field applied to each diodeis reversed on the movement of the key to the on or off state thecontrol ratio of the power supply becomes larger and it is moreeffective.

FIG. 7 illustrates still another circuit diagram of an embodimentaccording to the invention, wherein a magnetoresistor 2a is connected inseries between a power source 1 and a tone generator 4 and anothermagnetoresistor 2b is connected between the output side of themagnetoresistor 2a and ground, a potential divider being formed by saidtwo magnetoresistors 2a and 2b. The magnetoresistors aremagnetosensitive resistors the electric resistances of which increase asthe magnetic field increases. That is, the intensity of the magneticfield of the mag net 5 applied to the magnetoresistor 2a becomes amaximum and the intensity of the magnetic field of the magnet 5 appliedto the magnetoresistor 2b becomes a minimum when the key is in the offstate, and conversely, the intensity of the magnetic field of magnet 5applied to the magnetoresistor 2a becomes a minimum and the intensity ofthe magnetic field of magnet 5 applied to the magnetoresistor 2b becomesa maximum when the key is in the on state.

Accordingly, when the key is in the on state, a large amount of power issupplied to the tone generator 4, because the electric resistance of themagnetoresistor 2a is a minimum-and the electric resistance of themagnetoresistor 2b is a maximum.

Next, when the key is in the off state, hardly any voltage from thepower source 1 is supplied to the tone generator 4, and no sound isproduced, because the electric resistance of the magnetoresistor 2a is amaximum and the electric resistance of the magnetoresistor 2b is aminimum.

Generally, a magnetoresistor has some value of resistance even when nomagnetic field is applied to it, and furthermore, it is impossible todiminish the intensity of magnetic field applied to the magnetoresistor2b or zero owing to the structural limitation of the distance betweenthe magnetoresistors 2a and 2b. According to the present embodiment,however, even in such case, the electric voltage across the terminals ofthe magnetoresistor 2b becomes smalland the power source voltagesupplied to thetone generator 4 diminishes almost to zero, because theelectric resistances of the magnetoresistors 2a and 2b vary oppositelyand the electric resistance of the element 2a becomes large and thecontrol ratio of the tone generator becomes extremely large.

In the above description, although there is described the case where thekey is in the full on or off position, it will be understood that theamount of power supplied from the power source 1 to the tone generator 4varies in response to the extent the key is depressed, because thevalues of the resistances of the magnetoresistors 2a and 2b varydepending on the strength of the magnetic field which in turn varieswith the extent the key is depressed. Since the keys are spring loaded,such as by a spring 11 in FIG. 2, the output of the tone generator 4varies in accordance with the strength with which the key is depressed,and thus so-called touch-sensitive control can be effected.

FIG. 8 illustrates an arrangement of said magnet and saidmagnetoresistors, wherein the magnet 5 is fixed to the key 6 by anonmagnetic spacer 7, and the magnetoresistors 2a and 2b are fixed to aholder plate 10' which is mounted on the keyboard frame 9. Consequently,the magnetoresistors 2a and 2b are stationary and the magnet 5 moveswith the movement of the key 6. In this case, the magnet 5 and themagnetoresistors 2a and 2b are positioned as near to each other aspossible, and the intensity of the magnetic field of the magnet 5applied to the magnetoresistor 2a becomes a maximum and the intensity ofthe magnetic field of the magnet 5 applied to the magnetoresistor 2bbecomes a minimum when the key is in the off state, and the intensity ofthe magnetic field of the magnet 5 applied to the magnetoresistor 2abecomes a minimum and the intensity of the magnetic field of the magnet5 applied to the magnetoresistor 2b becomes a maximum when the key is inthe on state.

Furthermore, it is clear that the same functional effect is obtainedwhen the positions of the power source 1 and the tone generator 4 in thecircuit as shown in FIG. 7 are exchanged.

In the above embodiments, it will be understood that a plurality ofmagnets may be used instead of the multipolar magnet, and anelectromagnet may be used in place of a permanent magnet.

Although, in the above embodiments, the magnets are fixed to the keysand the magnetoresistors are fixed to the stationary parts, the samefunctional effects may be obtained even if the magnetoresistors arefixed to the keys and the magnets are fixed to the stationary parts.

As above described, the keying device of this invention is veryeffective practically, overcoming several prior art defects by switchingthe output of the tone generator without using any contacts, increasingthe reliability and reducing the complexity of the device itself.Moreover it provides a touch-sensitive control effect when the occasiondemands, and is able to provide a large control ratio.

The foregoing description contains a limited number of embodiments ofthe present invention. It will be understood, however, that suchembodiments are only illustrative and that numerous variations arepossible without departing from the purview of the invention as definedin the following claims.

What I claim is:

1. An electronic musical system comprising a DC electric power source, atone generator, a first resistance means connected in a series circuitbetween said power source and said tone generator, a second resistancemeans having one end connected to the series circuit between said firstresistance and said tone generator and the other end connected toground, at least one of said resistance means being a magnetoresistorthe electrical resistance of which varies in accordance with theintensity of the magnetic field applied thereto, a key means movablysupported in said system so as to be depressed when it is moved, and amagnet element mounted on said key means close to said magnetoresistorand movable therewith for controlling the electrical resistance of saidmagnetoresistor in accordance with the amount said key means isdepressed.

2. An electronic musical system as claimed in claim 1 wherein said firstresistance means is said magnetoresistor and said second resistancemeans is a fixed resistor.

3. An electronic musical system as claimed in claim 1 wherein said firstresistance means is a fixed resistor and said second resistance means issaid magnetoresistor.

4. An electronic musical system as claimed in claim 1 wherein both saidfirst and second resistance means are magfaces the other of said poleswhen said key means is depressed. 6. An electronic musical instrument asclaimed in claim 5 wherein said two poles are positioned parallel in ahorizontal direction.

7. An electronic musical instrument as claimed in claim 5 wherein saidtwo poles are arranged on a collinear vertical line.

1. An electronic musical system comprising a DC electric power source, atone generator, a first resistance means connected in a series circuitbetween said power source and said tone generator, a second resistancemeans having one end connected to the series circuit between said firstresistance and said tone generator and the other end connected toground, at least one of said resistance means being a magnetoresistorthe electrical resistance of which varies in accordance with theintensity of the magnetic field applied thereto, a key means movablysupported in said system so as to be depressed when it is moved, and amagnet element mounted on said key means close to said magnetoresistorand movable therewith for controlling the electrical resistance of saidmagnetoresistor in accordance with the amount said key means isdepressed.
 2. An electronic musical system as claimed in claim 1 whereinsaid first resistance means is said magnetoresistor and said secondresistance means is a fixed resistor.
 3. An electronic musical system asclaimed in claim 1 wherein said first resistance means is a fixedresistor and said second resistance means is said magnetoresistor.
 4. Anelectronic musical system as claimed in claim 1 wherein both said firstand second resistance means are magnetoresistors the electricalresistance of which varies in accordance with the intensity of magneticfield applied thereto, and said magnet element is positioned close toand controls both of said magnetoresistors so that the electricalresistance of said magnetoresistors varies oppositely from each other.5. An electronic musical instrument as claimed in claim 1 wherein saidmagnet element is a magnet having two opposite poles spaced from eachother, and said magnetoresistor faces one of said poles when said keymeans is not depressed and faces the other of said poles when said keymeans is depressed.
 6. An electronic musical instrument as claimed inclaim 5 wherein said two poles are positioned parallel in a horizontaldirection.
 7. An electronic musical instrument as claimed in claim 5wherein said two poles are arranged on a collinear vertical line.